Powerboats and other marine vessels are operatively powered by various types or configurations of marine drive systems. For example, in an inboard drive system, an inboard engine is completely located inside the hull of the vessel and rotates a driveshaft that extends through the hull and to which is attached the prop or propeller. In an outboard drive system, the engine and any shafts or gearing that connect the engine to the propeller are typically suspended over the transom or stern of the vessel such that the drive system is substantially disposed outboard of the hull. Recently, some drive systems of marine vessels have been configured to utilize one or more marine pod drive units, sometimes referred to azimuth thrusters. A marine pod drive unit typically includes an upper part or section that is fixedly disposed inboard of the vessel hull and a lower part or section that protrudes vertically through the bottom of the hull into the water and that supports the propeller in a generally horizontal orientation with respect to the hull. Further, the lower pod section is rotatably connected to the upper pod section so that it and the propeller can turn with respect to the upper pod section and the hull to steer the vessel. The motor and gearing to rotate the lower pod section with respect to the upper pod section may be disposed on the upper pod section along with clutches, transmission components, and the like to adjust the power output of the drive system.
To provide power to the marine pod drive unit, an internal combustion engine can be separately disposed inside the vessel hull and can be operatively connected to the upper pod section through a driveshaft. Possible advantages of physically separating the marine pod drive unit and the engine in this manner include that physical separation of components enables customized selection of different pod and engine combinations and that it protects the engine if the pod were to strike the seabed floor or underwater object. An example of this arrangement of a marine pod drive unit and an inboard engine is illustrated in FIG. 1 of U.S. Pat. No. 9,187,164 (“the '164 application”), which shows the inboard section of a marine pod drive unit receiving rotational power from a horizontally oriented driveshaft extending from the vessel's engine. The present disclosure is directed to a similar arrangement for transmitting rotational power from an inboard engine to a marine pod drive unit on a marine vessel.